If you were serious about promoting your business you would never ever rely on just one. If you "had to" you would select the SM platform that integrates with your off-line marketing focus and media.

Welcome,
I agree with all of the above to a degree. But if you consider 90% of all pre-purchase behaviour and research starts with a Search Engine, you want to set up Goolge My Business which allows you to rank better, have maps, direct messaging, products and services - FOR FREE.

Taz
Head Of Media & Strategy
https://truesydney.com.au/

Facebook Live. I believe there is a bigger audience that had access to it.

I would choose (and have chosen Periscope). I'm starting to post on it more regularly. I am interested in Blab, but I believe it is best used for a discussion (multiple people chatting at once) or having some of your customers give testimonials live during a session.

I really dig the Periscope integration with Twitter since Twitter is my main social media platform of choice for 2 of my ventures.

Go with google adword